FIGURE 3.

USA300ΔsaeP demonstrates increased transcript abundance of several known SaeR/S-virulence factors. (A) Mean fold-change of known SaeR/S-regulated virulence genes in USA300ΔsaeP and USA300ΔsaeQ relative to USA300 is shown. Transcript abundance was measured using TaqMan® RT-PCR at mid-exponential (ME; left) and early stationary (ES; right) phases of in vitro growth. Transcripts were normalized to gyrB and calibrated to transcript abundance in USA300. Data are from at least two independent experiments. (B) The USA300ΔsaeP strain of S. aureus produces significantly more Panton Valentine Leukocidin (PVL) compared to USA300. (Top) Representative Western blot of PVL protein in supernatants from S. aureus grown overnight. (Bottom) Quantification of PVL was calculated using densitometry as described in Materials and Methods. Data shown are amounts relative to USA300 and presented as the mean ± SEM of three independent experiments. *P ≤ 0.05 One-Way ANOVA with Tukey’s post-test. n.d., not detected.